After the publication of her 24th novel, Joyce Carol Oates was invited to appear on the Oprah Winfrey show. The book, We Were the Mulvaneys, had been chosen as one of Oprah's coveted Book Club titles and a portion of the show was devoted to whooping her achievement. Even by the standards of the format, it was a bizarre encounter - the booming, vivacious pioneer of confessional TV and the small, nervy academic. After the recording, an astonished Oates was mobbed by a gang of ardent Book Club members, one of whom threw her arms about her and said: "If my daughter had read your novel she would not have committed suicide."

Oates belongs to a different world, one in which books are "texts" to be studied, not lifebuoys to be clung to. The Princeton professor has created a series of dense and complicated novels which she says are "architecturally structured" and which she maps out in her mind, like movies, before committing them, longhand, to paper. She does not have a computer; she does not use the internet. It is often remarked that she saves all her energy for the life of her mind, and during our interview she maintains an almost plant-like composure. With a build so fragile and skin that glows like a lychee, it seems plausible that the use of flash-photography might reduce Oates to a little pile of chalk dust. Only her eyes skim about with vigour, goggling like those of a deep-sea fish.

The irony - and Oates is fond of ironies; they amuse her - is that she and the all-conquering Oprah do not come from such vastly different backgrounds. Oates was born in 1938 to a factory worker and a hard-working housewife - a couple whose frustrated ambitions she speaks of with her face turned tactfully away. "He might've been a teacher," she says. "He was such an avid reader. He loved to read. He loved Charles Dickens, for instance. But he had to work in a factory in the 1930s and he stayed there for 40 years. The depression. A long time ago."

Despite her success (Oates has published 37 novels, 19 collections of short stories, four novellas, eight volumes of poetry, seven plays and eight academic essays), she has the habit of hitching the disclaimer "it seems like a small thing in the great scale of being" to the end of her statements, although this is possibly a rebuke to the giant egos of the literary world rather than straightforward modesty. The great scale of being is something she is in two minds about. "I veer between a vision of the human race rather like Jonathan Swift's, dark and embittered and satirical, and a kind of idealism that maybe there are just enough wonderful people in the world to make us feel thrilled with the possibilities of the human."

Her latest book, Middle Age: A Romance, introduces just such a character, Adam Berendt, who dies trying to save a young girl from drowning. Berendt enters the wealthy New York suburb of Salthill-on-Hudson and, through the pureness of his heart, persuades its avaricious residents that it is not too late to change. Middle Age is intensely realistic, a facsimile of fraught modern America, particularly the women in it, "who are accustomed to not seeing imperfections in men, though anxiously aware of the smallest imperfections in themselves". Oates was amazed when some critics read it as a piece of satire. "When most people write about the suburbs of America, particularly the women of the upper middle class, they're very satirical and harsh. But I know these women and I see no justification for being cruel to them. They're actually very wonderful people. Some reviewer made the point that the characters were despicable, but that the author showed compassion for them, whereas I didn't feel they were despicable at all. In a world in which there are serial killers and genocide, these people are basically well intentioned."

Good intentions matter to Oates. She regrets the lack of "morality and old-fashioned values" in America's "trash" culture, and by old-fashioned she means Socrates, not Reagan. Oates values what she calls "small gestures with a strong ethical component", such as being kind to mistreated animals. She is big on compassion. During the Vietnam war, she and her husband, an editor (he also has a PhD in 18th-century literature, she adds), moved to Canada for 10 years in protest. At the age of 64, she is not considering a repeat move in protest against George Bush's likely war with Iraq, but his belligerence appals her, as does his "exploitation" of American patriotism for political ends. To her regret, she feels there is little she can do. "There's a small intellectual minority in the United States with almost no influence." She smiles sadly. "I hate to say it."

Writing makes Oates melancholy, especially towards the end of a book, when the momentum propels her through 10-hour days. She needs to surround herself with people to relax. So it was that, in spite of disliking most television and finding popular culture "debased", Oates took to Oprah's Book Club in a way some of her younger, more modish literary peers did not. In Oprah's world, readers don't read; they stay up all night sobbing their way through a book and then write to its author in the morning. "I found that very wonderful and very surprising," says Oates, blinking her great marble eyes. "Since I'm a literary person, I look upon books as texts that have been imagined and written. But the general reading public looks upon books as documents of reality, and so the people on Oprah would say, for instance, 'I have a mother just like that.' Or, 'My father was just like that.' Or, 'This happened to me.' They don't seem to perceive - nor do they wish to perceive - that this is a novel. I think if they had, for instance, a class on Shakespeare's Hamlet, they would say, 'Gertrude is just like my mother; Hamlet's like my brother; Ophelia, that's my story.' And they would get a lot of emotion out of that." She falters. There is nothing wrong with reading as therapy, but there is something perhaps painful to an author in seeing readers gobble up their books as an excuse to "basically talk about themselves". Oates's eyelashes lower. "Of course, one doesn't want to dampen that enthusiasm."

Why, I ask, did Jonathan Franzen, author of The Corrections, refuse to have his book recommended by Oprah? "Well, he ultimately apologised to Oprah, but she wouldn't accept his apology because she was wounded in her pride." She pauses. "It was also a gender thing, because I think that Jonathan Franzen perceives the Oprah book readers as mainly women, and he would prefer a male readership." This softly delivered grenade hangs deliciously in the air for a second, then evaporates.

Among Oates's heroes are Franklin Roosevelt and Abraham Lincoln. When asked if she has ever been heroic herself, she says: "Oh, oh, that's very interesting. It would probably be in such a private way that it wouldn't be... I don't think I could really say. I'd feel self-conscious. Maybe someone else could say." She refers most intimate questions back to her books, as to a set of universal truths, although it is really the personal that inspires her. "It sounds sentimental, but I feel that the real heroes in the world are not the famous people but the people in our own families, people who never wrote a book, never published an article, never painted a picture, but who have made a household with what is sometimes the highest measure of creativity. They don't get any credit for it. But there it is, a complete story."